Understanding Kramers turnover by means of molecualr dynamics simulation

Abstract

The cis-trans isomerization rate of 4-dimethylamino-4'-nitroazobenzene (DNAB) was analyzed using molecular dynamics (MD) simulation for long runs. In high viscosity solvents, the reaction rate is retarded gradually as the system pressure approaches ten MPa (Kramers turnover). The interesting behavior was theoretically modeled based on the reaction rate theories in condensed phase, i.e., Kramers theory, Kramers-Grote-Hynes theory, Pollak-Glabert-Hanggi theory. The rate computationally evaluated using Accelerated MD (AMD), which can boost the isomerization process to directly obtain the reaction rate.